Described below is a method of scheduling of packets in a mobile communication system.
In mobile radio systems, where dynamic assignment of radio capacity amongst user equipments (UEs) operates in the uplink, for example universal mobile telecommunication system (UMTS) enhanced uplink dedicated channel (E-DCH) transmission, for efficiency reasons, radio resources that are to be used within a time period can be assigned on a UE basis, rather than on the basis of the individual bearers that a UE is using to transmit data. This then requires that the UE apply a rule regarding how much capacity is assigned to each bearer within the time period, for example, between bearers assigned to signalling, speech and best effort data services.
For UMTS E-DCH the rule that has been used is the following. For each transmission opportunity, i.e. transmission time interval (TTI), the scheduler allocates capacity to the highest priority bearer that has a non-empty transmission buffer. The principle is highest priority first, but unfortunately, at times of high cell load, when the UE may not be assigned all of the capacity that the data buffered for all bearers requires, this can lead to starvation of the lower priority bearers.
For UMTS long term evolution (LTE) uplink transmission there is a desire that starvation be avoided and greater flexibility in resource assignment between bearers be possible, whilst retaining the per UE, rather than per UE bearer, resource allocation.
One proposal for assigning capacity has been to assign resources to each bearer, in priority order, until each has received an allocation equivalent to the minimum data rate for that bearer, after which any additional capacity is assigned to bearers in, for example, priority order.